1. Technical Field
The present invention relates to a semiconductor device that is capable of transferring electric signals between two circuits to which electric signals having different potentials from each other are input.
2. Related Art
To transfer electric signals between two circuits to which electric signals having different potentials from each other are input, photo couplers are often used. Each photo coupler includes a light emitting element such as a light emitting diode and a light receiving element such as a photo transistor. The light emitting element converts an input electric signal into light, and the light receiving element returns the light to an electric signal. In this manner, photo couplers transfer electric signals.
However, it is difficult to reduce the size of each photo coupler due to the existence of the light emitting element and the light receiving element. Also, where the frequency of electric signals is high, the photo couplers cannot follow the electric signals. To counter these problems, there has been a technique for transmitting electric signals by inductively coupling two inductors, as disclosed in Japanese translation of PCT international application NO. 2001-513276, for example.
A structure in which pairs of inductors are used when a first semiconductor chip on the transmission side and a second semiconductor chip on the reception side are connected to each other through a transmission path is disclosed in Japanese Laid-open patent publication NO. 2008-113093. More specifically, the transmission line and the first semiconductor chip are connected in a noncontact manner by electromagnetically coupling the pair of inductors on the transmission side. The transmission line and the second semiconductor chip are connected in a noncontact manner by electromagnetically coupling the pair of inductors on the reception side.
The present inventor has recognized as follows. Where a transmission-side circuit and a reception-side circuit are connected through an interconnect substrate, the transmission-side circuit and the interconnect substrate may be connected by a pair of inductors, and the interconnect substrate and the reception-side circuit may be connected by a pair of inductors. In such a case, two pairs of inductors are used. Therefore, there is a possibility that signal attenuation occurs while signals are being transferred, and the signals cannot be transferred accurately. To transfer signals accurately, the distance between two inductors forming the pairs of inductors may be made shorter. However, where the reference voltage of the transmission-side circuit and the reference voltage of the reception-side circuit differ from each other, insulation between the transmission-side circuit and the reception-side circuit cannot be secured, if the distance between the two inductors forming the pairs of inductors is made shorter at each two pairs of inductors. Therefore, it is difficult to secure insulation between the transmission-side circuit and the reception-side circuit while signals are being transferred accurately.